Dual pump system and control thereof

ABSTRACT

A pump system includes: first and second flow paths connected with a common inlet and a common outlet, and disposed in parallel with each other; the first flow path having a first aspirate valve, a first pump in series with and downstream of the first aspirate valve, and a first dispense valve in series with and downstream of the first pump; the second flow path having a second aspirate valve, a second pump in series with and downstream of the second aspirate valve, and a second dispense valve in series with and downstream of the second pump; the first aspirate valve, the first pump, and the first dispense valve of the first flow path, being configured to operate in both a dispense and aspirate modes; the second aspirate valve, the second pump, and the second dispense valve of the second flow path, being configured to operate in both a dispense and aspirate modes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 62/629,993, filed Feb. 13, 2018, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to a pump system, particularly to a dual pump system, and more particularly to the control of a dual pump system.

Known in the art are dual pump systems having configurations as disclosed in U.S. Pat. Nos. 4,359,312, 5,145,339, 5,253,981, 5,026,255, and 5,637,208. In a dual pump system, a typical arrangement is to have one pump dispense while another pump aspirates. During the transition time (transition zone) where the dispensing action switches from one pump to another pump, negative and positive pressure disturbances or spikes typically occur, also referred to as cross over pulses, resulting in non-continuous fluid flow at a defined constant flow rate. While these pressure spikes may be acceptable for some applications, other applications, such as medical applications, demand a higher level of performance.

While existing dual pump systems may be suitable for their intended purpose, the art relating to a dual pump system would be advanced with an arrangement of fluid flow control devices and control thereof to produce continuous or substantially continuous fluid flow at a defined constant flow rate during the transition of dispensing from one pump to dispensing from another pump.

BRIEF DESCRIPTION OF THE INVENTION

In an embodiment, a pump system includes: a first fluid flow path in fluid flow connection with an inlet path and an outlet path; a second fluid flow path in fluid flow connection with the inlet path and the outlet path; the first and second fluid flow paths being fluidly disposed in parallel with each other; the first fluid flow path having a first aspirate valve, a first pump disposed in series with and downstream of the first aspirate valve, and a first dispense valve disposed in series with and downstream of the first pump; the second fluid flow path having a second aspirate valve, a second pump disposed in series with and downstream of the second aspirate valve, and a second dispense valve disposed in series with and downstream of the second pump; wherein the first aspirate valve, the first pump, and the first dispense valve of the first fluid flow path, are configured to operate in both a dispense mode of operation and an aspirate mode of operation; wherein the second aspirate valve, the second pump, and the second dispense valve of the second fluid flow path, are configured to operate in both a dispense mode of operation and an aspirate mode of operation.

Another embodiment includes a control module for controlling a dual pump system having a first fluid flow path having a series combination of a first aspirate valve, a first pump, and a first dispense valve, and a second fluid flow path having a series combination of a second aspirate valve, a second pump, and a second dispense valve, the first and second fluid flow paths being fluidly disposed in parallel with each other and having a common inlet path and a common outlet path, the control module having a processing circuit responsive to executable instructions which when executed by the processing circuit is configured to adjust the first aspirate valve, the first pump, the first dispense valve, the second aspirate valve, the second pump, and the second dispense valve, according to the following method: in a first instance, facilitate a transition of dispensing from the second fluid flow path to dispensing from the first fluid flow path, wherein in the first instance the first pump starts ramping up in speed from a waiting state, wherein in the first instance the first aspirate valve is open, the first dispense valve is closed, the second aspirate valve is closed, and the second dispense valve is open; in a second instance subsequent to the first instance, facilitate dispensing in the first fluid flow path while the second fluid flow path finishes dispensing, wherein in the second instance the first pump is nearing the end of its ramping up in speed and the second pump is ramping down in speed, wherein in the second instance both the first dispense valve and the second dispense valve are open, and both the first aspirate valve and the second aspirate valve are closed; and in a third instance subsequent to the second instance, facilitate dispensing in only the first fluid flow path, wherein in the third instance the first pump is dispensing and the second pump is ramping down in speed, wherein in the third instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the third instance the second dispense valve is closed and the second aspirate valve open.

The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the exemplary non-limiting drawings wherein like elements are numbered alike in the accompanying Figures:

FIG. 1 depicts a block diagram schematic of a pump system having a variety of fluid flow control devices and a single reservoir, in accordance with an embodiment;

FIG. 2 depicts a block diagram schematic of a pump system alternative to that of FIG. 1, with two reservoirs, in accordance with an embodiment;

FIG. 3 depicts a block diagram schematic of a pump system alternative to that of FIGS. 1-2, with optionally more than two reservoirs, in accordance with an embodiment;

FIGS. 4A and 4B depict, in combination, a state diagram for corresponding ones of the fluid flow control devices of FIGS. 1-3, in accordance with an embodiment;

FIG. 5 depicts an example motion diagram for a single pump cycle with the on-off state diagrams for the corresponding aspirate and dispense valves, in accordance with an embodiment;

FIG. 6 depicts an example motion diagram for a dual pump cycle with the on-off state diagrams for the corresponding aspirate and dispense valves, in accordance with an embodiment;

FIG. 7 depicts a first resulting output pressure, in accordance with an embodiment;

FIG. 8 depicts a second resulting output pressure, in accordance with an embodiment; and

FIG. 9 depicts a third resulting output pressure, in accordance with an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Although the following detailed description contains many specifics for the purposes of illustration, anyone of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the claims. Accordingly, the following example embodiments are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.

An embodiment, as shown and described by the various figures and accompanying text, provides a dual pump system and control thereof, with the two pumps fluidly disposed in parallel with each other, for producing continuous or substantially continuous fluid flow at a defined constant flow rate during each pump cycle and during the transition of fluid dispensing from a first pump and then from a second pump. In general, the dual pump system uses positive displacement pumps, such as piston pumps, syringe pumps, bellows pumps, etc. As used herein, the term continuous or substantially continuous fluid flow at a defined constant flow rate means fluid flow that permits for a duration of a pressure disturbance in the transition zone to be is equal to or less than 5%, and in an embodiment on the order of about 1%, of an overall single dispense cycle for a given pump. To achieve the continuous or substantially continuous fluid flow at a defined constant flow rate, a first pump is set for dispensing while a second pump is set for aspirating, then a switch over occurs so that the first pump is set for aspirating while the second pump is set for dispensing, and during each switch over event both pumps are dispensing simultaneously for a defined period of time, which is herein referred to as a phase overlap. In a pre-phase overlap event, one pump starts ramping up in speed but does not yet dispense. During a phase overlap event, the one pump that has ramped up in speed now starts dispensing, while the other pump, still dispensing but near the end of its dispense stroke, is ramping down in speed. In a post-phase overlap event, the pump that ramps down then aspirates, which is at a faster rate than a dispense rate of the dispensing pump. At the end of the aspiration time period, the aspirating pump is put on hold until it is called on to dispense. When the dispensing pump nears the end of its dispense stroke, it then starts ramping down in speed and the awaiting pump (the pump on hold) starts dispensing. The transition from one pump dispensing to another pump dispensing is initiated by the pre-phase overlap event where the waiting pumps starts ramping up in speed. This initiation point in the pumping sequence is a trigger point at which a controller commences the switch over from the one pump to the other pump. The foregoing two-pump dispense cycle repeats as needed until stopped. With appropriate control of the trigger points, the phase overlap time durations, and the timing of the aspiration and dispense events, continuous or substantially continuous fluid flow at a defined constant flow rate is achievable. An example application for an embodiment disclosed herein is a medical application requiring continuous flow of equal to or less than 10 milliliters per minute at equal to or less than 30 psi (pounds per square inch).

An embodiment as disclosed herein is absent any check valves, and instead uses active aspirate and dispense valves that can be controlled by a controller, where the controller determines when the valves open and close. This degree of control is advantageous when ramping up and ramping down a pump during a pump cycle, as the ramping up/down portion typically has a non-linear component since this is where the acceleration phase of the pump cycle is. With active valves, it is possible to alter the timing of the valve action to adjust the pump cycle as needed, which is discussed further herein below.

FIG. 1 depicts a pump system 100 having a first fluid flow path 200 in fluid flow connection with an inlet path 102 and an outlet path 104, and a second fluid flow path 300 in fluid flow connection with the inlet path 102 and the outlet path 104. The first and second fluid flow paths 200, 300 are fluidly disposed in parallel with each other. In an embodiment, the first fluid flow path 200 includes a first aspirate valve 202, a first pump 204 disposed in series with and downstream of the first aspirate valve 202, and a first dispense valve 206 disposed in series with and downstream of the first pump 204. In an embodiment, the second fluid flow path 300 includes a second aspirate valve 302, a second pump 304 disposed in series with and downstream of the second aspirate valve 302, and a second dispense valve 306 disposed in series with and downstream of the second pump 304. In an embodiment, one or more of the first aspirate valve 202, the first dispense valve 206, the second aspirate valve 302, and the second dispense valve 306 are diaphragm valves. It is contemplated, however, that other non-diaphragm valves may be suitable for a purpose disclosed herein, but for a medical application it has been found that diaphragm valves are easier to clean and purge when needed. In an embodiment, the first aspirate valve 202, the first pump 204, and the first dispense valve 206 of the first fluid flow path 200, are configured to operate in both a dispense mode of operation and an aspirate mode of operation, and the second aspirate valve 302, the second pump 304, and the second dispense valve 306 of the second fluid flow path 300, are configured to operate in both a dispense mode of operation and an aspirate mode of operation, in accordance with an embodiment disclosed herein. In an embodiment, the first pump 204 is driven by a stepper motor 208, and the second pump 304 is driven by a stepper motor 308. It is contemplated, however, that other non-stepper motor drivers may be suitable for a purpose disclosed herein, such as servos or linear motors that have the ability to control acceleration and speed, but for a medical application it has been found that stepper motors provide a high precision of operation. Alternatively, DC or AC motor drives with position feedback are also contemplated. In an embodiment, the outlet path 104 includes a fluid flow restrictor 106, which serves to reduce output flow pressure variations resulting from the frequency of operation of the stepper motors 208, 308. In an embodiment, the inlet path 102 is connected to or configured to receive fluid 108 from a fluid reservoir 110. In an embodiment, the fluid reservoir 110 may be elevated so as to provide hydraulic head to prevent air bubbles from forming on the aspiration side of the system 100. While FIG. 1 depicts the system 100 as an aspirate or suction type system where the fluid 108 is sucked out of the reservoir 110, it will be appreciated that an embodiment may also employ a pressurized reservoir 110 without detracting from the scope of the invention disclosed herein. In the case of a pressurized system, the timing of the aspirate and dispense valves would be altered to reduce the transition pressure spikes, as the response times for a diaphragm valve under pressure are different than under suction.

FIG. 2 depicts a pump system 100A that is similar but alternative to the pump system 100 of FIG. 1, where the pump system 100A employs two separate fluid reservoirs 110A, 110B instead of a single reservoir 110. Otherwise, the pump system 100A operates as described above in connection with the pump system 100.

FIG. 3 depicts a pump system 100B that is similar but alternative to the pump systems 100, 100A of FIGS. 1 and 2, respectively, where the pump system 100B optionally employs more than two separate fluid reservoirs 110A, 110B, 110′ instead of a single reservoir 110 or a dual reservoir 110A, 110B. Otherwise, the pump system 100B operates as described above in connection with the pump system 100. As depicted in FIG. 3, a third or more reservoir 110′, and a third or more fluid flow path 200′, are denoted by prime reference numerals, with the associated fluid flow components (aspirate valve 202′, pump 204′, dispense valve 206′, and stepper motor 208′, for example) being depicted in dashed line fashion with corresponding prime reference numerals.

In an embodiment, the pump system 100 further includes a control module 400 having a processing circuit 402 responsive to executable instructions which when executed by the processing circuit 402 is configured to communicate with and adjust the first aspirate valve 202, the first pump 204, the first dispense valve 206, the second aspirate valve 302, the second pump 304, and the second dispense valve 306, via a hardwire or optical communication port 406, or a wireless connection 404, and according to a software or firmware method 500, see FIGS. 4A, 4B, and 5-6, Operational Sequence-1 (described below), and Operational Sequence-2 (described below), for example, programmed into the control module 400. In FIGS. 4A, 4B, and 5-6, any reference to P1 and P2 is in reference to the associated pump and/or valves of Pump 1 (first pump 204) and Pump 2 (second pump 304), respectively. A graphical user interface, GUI, 408 on the control module 400 may be used to enter control information into the control module 400 and to receive visual information relating to the functioning of the control module 400 and the pump system 100. In a first instance, the method 500 facilitates a transition of dispensing from the second fluid flow path 300 to dispensing from the first fluid flow path 200, wherein in the first instance the first pump 204 starts ramping up in speed from a waiting state, wherein in the first instance the first aspirate valve 202 is open, the first dispense valve 206 is closed, the second aspirate valve 302 is closed, and the second dispense valve is open (see FIG. 4A, time duration 520). In a second instance subsequent to the first instance, the method 500 facilitates dispensing in the first fluid flow path 200 while the second fluid flow path 300 finishes dispensing, wherein in the second instance the first pump 204 is nearing the end of its ramping up in speed and the second pump 304 is ramping down in speed, wherein in the second instance both the first dispense valve 206 and the second dispense valve 306 are open, and both the first aspirate valve 202 and the second aspirate valve 302 are closed (see FIG. 4A, time duration 522). In a third instance subsequent to the second instance, the method 500 facilitates dispensing in only the first fluid flow path 200, wherein in the third instance the first pump 204 is dispensing and the second pump 304 is ramping down in speed, wherein in the third instance the first dispense valve 206 is open and the first aspirate valve is closed 202, and wherein in the third instance the second dispense valve 306 is closed and the second aspirate valve open 302 (see FIG. 4A, time duration 524). In a fourth instance subsequent to the third instance, the method continues to facilitate dispensing in only the first fluid flow path 200, wherein in the fourth instance the first pump 204 is dispensing and the second pump 304 is aspirating, wherein in the fourth instance the first dispense valve 206 is open and the first aspirate valve 202 is closed, and wherein in the fourth instance the second dispense valve 306 is closed and the second aspirate valve 302 is open (see FIG. 4A, time duration 526). In a fifth instance subsequent to the fourth instance, the method continues to facilitate dispensing in only the first fluid flow path 200, wherein in the fifth instance the first pump 204 is dispensing and the second pump 304 is waiting, wherein in the fifth instance the first dispense valve 206 is open and the first aspirate valve 202 is closed, and wherein in the fifth instance the second dispense valve 306 is closed and the second aspirate valve 302 is open (see FIG. 4A, time duration 528). In a sixth instance subsequent to the fifth instance, the method facilitates a transition of dispensing from the first fluid flow path 200 to dispensing from the second fluid flow path 300, wherein in the sixth instance the second pump 304 starts ramping up in speed from a waiting state while the first pump 204 is dispensing, wherein in the sixth instance the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second aspirate valve 302 is open, and the second dispense valve is closed (see FIG. 4B, time duration 530). In a seventh instance subsequent to the sixth instance, the method facilitates dispensing in the second fluid flow path 300 while the first fluid flow path 200 finishes dispensing, wherein in the seventh instance the first pump 204 is ramping down in speed and the second pump 304 is nearing the end of its ramping up in speed, wherein in the seventh instance both the first dispense valve 206 and the second dispense valve 306 are open, and both the first aspirate valve 202 and the second aspirate valve 302 are closed (see FIG. 4B, time duration 532). In an eighth instance subsequent to the seventh instance, the method facilitates dispensing in only the second fluid flow path 300, wherein in the eighth instance the first pump 204 is ramping down in speed and the second pump 304 is dispensing, wherein in the eighth instance the second dispense valve 306 is open and the second aspirate valve is closed 302, and wherein in the eighth instance the first dispense valve 206 is closed and the first aspirate valve 202 is open (see FIG. 4B, time duration 534). In a ninth instance subsequent to the eighth instance, the method continues to facilitate dispensing in only the second fluid flow path 300, wherein in the ninth instance the second pump 304 is dispensing and the first pump 204 is aspirating, wherein in the ninth instance the second dispense valve 306 is open and the second aspirate valve 302 is closed, and wherein in the ninth instance the first dispense valve 206 is closed and the first aspirate valve 202 is open (see FIG. 4B, time duration 536). In a tenth instance subsequent to the ninth instance, the method continues to facilitate dispensing in only the second fluid flow path 300, wherein in the tenth instance the second pump 304 is dispensing and the first pump 204 is waiting, wherein in the tenth instance the second dispense valve 306 is open and the second aspirate valve 302 is closed, and wherein in the tenth instance the first dispense valve 206 is closed and the first aspirate valve 202 is open (see FIG. 4B, time duration 538). In an eleventh instance subsequent to the tenth instance, the pumping cycle loops back to repeat the first through tenth instances (see FIGS. 4A and 4B, repetitive loop from time duration 538 to time duration 520). In an embodiment, the dispense action employed herein involves the dispensing of the fluid 108 from the reservoir 110 via the inlet and outlet paths 102, 104, and via one or both of the first and second fluid flow paths 200, 300 (see FIG. 1 for example). In another embodiment, the dispense action employed herein involves the dispensing of the fluid 108A, 108B from the reservoirs 110A, 110B, respectively, via the inlet and outlet paths 102A, 102B, 104, and via one or both of the first and second fluid flow paths 200, 300 (see FIG. 2 for example). In another embodiment, the dispense action employed herein involves the dispensing of the fluid 108A, 108B, 108′ from the reservoirs 110A, 110B, 110′, respectively, via the inlet and outlet paths 102A, 102B, 102′, 104, and via one or more of the fluid flow paths 200, 300, 200′ (see FIG. 3 for example).

From the foregoing, it will be appreciated that an embodiment as disclosed herein may include a single reservoir from which two or more fluid flow paths may be connected, two or more reservoirs from which two or more fluid flow path may be correspondingly connected, multiple (two, three, four, or more) reservoirs from which multiple (two, three, four, or more) fluid flow paths may be correspondingly connected, a single reservoir from which multiple (two, three, four, or more) fluid flow paths may be connected, or any combination of the foregoing arrangements.

Reference is now made to FIGS. 4A and 4B in further detail, which depicts a state diagram (method) 500 of the various fluid flow control devices of the pump system 100. For example, line 502 denotes the state of the first aspirate valve 202, line 504 denotes the state of the first pump 204, line 506 denotes the state of the first dispense valve 206, line 512 denotes the state of the second aspirate valve 302, line 514 denotes the state of the second pump 304, and line 516 denotes the state of the second dispense valve 306.

In time duration 520, which is just prior to a phase overlap event, the first pump 204 is ramping up in speed, the first aspirate valve 202 is open, the first dispense valve 206 is closed, the second pump 304 is dispensing, the second aspirate valve 302 is closed, and the second dispense valve 306 is open.

In time duration 522, which is during a phase overlap event where both the first and the second fluid flow paths 200, 300 are dispensing, the first pump 204 is still ramping up in speed, the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second pump 304 is ramping down in speed, the second aspirate valve 302 is closed, and the second dispense valve 306 is open.

In time duration 524, which is during a dispense event via the first fluid flow path 200, the first pump 204 is dispensing, the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second pump 304 is still ramping down in speed, the second aspirate valve 302 is open, and the second dispense valve 306 is closed.

In time duration 526, which is still during a dispense event via the first fluid flow path 200, the first pump 204 is dispensing, the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second pump 304 is aspirating, the second aspirate valve 302 is open, and the second dispense valve 306 is closed.

In time duration 528, which is still during a dispense event via the first fluid flow path 200, the first pump 204 is dispensing, the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second pump 304 is waiting (on hold), the second aspirate valve 302 is open, and the second dispense valve 306 is closed.

In time duration 530, which is just prior to a phase overlap event, the first pump 204 is dispensing, the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second pump 304 is ramping up in speed, the second aspirate valve 302 is open, and the second dispense valve 306 is closed.

In time duration 532, which is during a phase overlap event where both the first and the second fluid flow paths 200, 300 are dispensing, the first pump 204 is ramping down in speed, the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second pump 304 is ramping up in speed, the second aspirate valve 302 is closed, and the second dispense valve 306 is open.

In time duration 534, which is during a dispense event via the second fluid flow path 300, the first pump 204 is still ramping down in speed, the first aspirate valve 202 is open, the first dispense valve 206 is closed, the second pump 304 is dispensing, the second aspirate valve 302 is closed, and the second dispense valve 306 is open.

In time duration 536, which is still during a dispense event via the second fluid flow path 300, the first pump 204 is aspirating, the first aspirate valve 202 is open, the first dispense valve 206 is closed, the second pump 304 is dispensing, the second aspirate valve 302 is closed, and the second dispense valve 306 is open.

In time duration 538, which is just prior to a phase overlap event, the first pump 204 is waiting (on hold), the first aspirate valve 202 is open, the first dispense valve 206 is closed, the second pump 304 is dispensing, the second aspirate valve 302 is closed, and the second dispense valve 306 is open.

After time duration 538, the cycling sequence loops back to time duration 520, and the dispensing process continues cycling through time duration steps 520 to 538 until stopped. By employing the aforementioned sequence of events to the fluid flow control devices of the pump system 100 via the state diagram (method) 500, continuous or substantially continuous fluid flow at a defined constant flow rate is achievable.

As noted herein above, the ramping up/down portion of a pump cycle typically has a non-linear component due to the acceleration/deceleration phase of the corresponding pump, and that it is possible to alter the timing of the valve action to adjust the pump cycle as needed. For example, in time duration 532 that follows 530, it is possible to keep the second aspirate valve 302 of the second pump 304 open for a beginning portion of time duration 532 even though the second pump 304 is displacing fluid, where the fluid on the downstream side of the second pump 304 would return to the reservoir 110 until the second pump 304 is at full dispense speed, at which time the controller 400 would change the state of the second aspirate valve 302 to be closed. Likewise in the case of the first pump 204, it is possible to close the first dispense valve 206 and open the first aspirate valve 202 before the ramp down of the first dispense pump 204 was started, which would cause the ramp down fluid on the downstream side of the first pump 204 to be directed to the reservoir 110 via the first fluid flow path 200. Under this type of operation, the acceleration and deceleration parts of the cycle could be skipped in the pump cycle.

From the foregoing, it will be appreciated that in a first duration of time 524, 526, 528 the first fluid flow path 200 is configured to be in a dispense mode of operation while the second fluid flow path 300 is configured to be in an aspirate mode of operation, and in a second duration of time 534, 536, 538 the first fluid flow path 200 is configured to be in an aspirate mode of operation while the second fluid flow path 300 is configured to be in a dispense mode of operation. During the dispense mode of operation of the first fluid flow path 200, the first dispense valve 206 is open and the first aspirate valve 202 is closed. During the dispense mode of operation of the second fluid flow path 300, the second dispense valve 306 is open and the second aspirate valve 302 is closed. During the aspirate mode of operation of the first fluid flow path 200, the first dispense valve 206 is closed and the first aspirate valve 202 is open. During the aspirate mode of operation of the second fluid flow path 300, the second dispense valve 306 is closed and the second aspirate valve 302 is open. In a third duration of time 522, 532 both the first fluid flow path 200 and the second fluid flow path 300 are configured to be in a dispense mode of operation. During the third duration of time, both the first and second dispense valves 206, 306 are open, and both the first and second aspirate valves 202, 302 are closed. As noted herein above, the third duration of time is herein referred to as a phase overlap.

In an embodiment, the first aspirate valve 202, the first dispense valve 206, the second aspirate valve 302, and the second dispense valve 306, all have adjustable open and close times that are controlled via the control module 400 via software or firmware programming of executable instructions. In an embodiment, both the first pump 204 and the second pump 304 have adjustable speed and acceleration characteristics that are controlled via the control module 400 via software or firmware programming of executable instructions. And in an embodiment, the third duration of time is adjustable in duration by the control module 400 via software or firmware programming of executable instructions.

In view of the foregoing, it will be appreciated that an embodiment includes a control module 400 for controlling a dual pump system 100 having a first fluid flow path 200 having a series combination of a first aspirate valve 202, a first pump 204, and a first dispense valve 206, and a second fluid flow path 300 having a series combination of a second aspirate valve 302, a second pump 304, and a second dispense valve 306, the first and second fluid flow paths 200, 300 being fluidly disposed in parallel with each other and having a common inlet path 102 and a common outlet path 104, the control module 400 having a processing circuit 402 responsive to executable instructions which when executed by the processing circuit 402 is configured to adjust the first aspirate valve 202, the first pump 204, the first dispense valve 206, the second aspirate valve 302, the second pump 304, and the second dispense valve 306, according to the following method: in a first instance, facilitate a transition of dispensing from the second fluid flow path 300 to dispensing from the first fluid flow path 200, wherein in the first instance the first pump 204 starts ramping up in speed from a waiting state, wherein in the first instance the first aspirate valve 202 is open, the first dispense valve 206 is closed, the second aspirate valve 302 is closed, and the second dispense valve is open (see FIG. 4A, time duration 520); in a second instance subsequent to the first instance, facilitate dispensing in the first fluid flow path 200 while the second fluid flow path 300 finishes dispensing, wherein in the second instance the first pump 204 is nearing the end of its ramping up in speed and the second pump 304 is ramping down in speed, wherein in the second instance both the first dispense valve 206 and the second dispense valve 306 are open, and both the first aspirate valve 202 and the second aspirate valve 302 are closed (see FIG. 4A, time duration 522); in a third instance subsequent to the second instance, facilitate dispensing in only the first fluid flow path 200, wherein in the third instance the first pump 204 is dispensing and the second pump 304 is ramping down in speed, wherein in the third instance the first dispense valve 206 is open and the first aspirate valve is closed 202, and wherein in the third instance the second dispense valve 306 is closed and the second aspirate valve open 302 (see FIG. 4A, time duration 524). In a fourth instance subsequent to the third instance, the method continues to facilitate dispensing in only the first fluid flow path 200, wherein in the fourth instance the first pump 204 is dispensing and the second pump 304 is aspirating, wherein in the fourth instance the first dispense valve 206 is open and the first aspirate valve 202 is closed, and wherein in the fourth instance the second dispense valve 306 is closed and the second aspirate valve 302 is open (see FIG. 4A, time duration 526). In a fifth instance subsequent to the fourth instance, the method continues to facilitate dispensing in only the first fluid flow path 200, wherein in the fifth instance the first pump 204 is dispensing and the second pump 304 is waiting, wherein in the fifth instance the first dispense valve 206 is open and the first aspirate valve 202 is closed, and wherein in the fifth instance the second dispense valve 306 is closed and the second aspirate valve 302 is open (see FIG. 4A, time duration 528). In a sixth instance subsequent to the fifth instance, the method facilitates a transition of dispensing from the first fluid flow path 200 to dispensing from the second fluid flow path 300, wherein in the sixth instance the second pump 304 starts ramping up in speed from a waiting state while the first pump 204 is dispensing, wherein in the sixth instance the first aspirate valve 202 is closed, the first dispense valve 206 is open, the second aspirate valve 302 is open, and the second dispense valve is closed (see FIG. 4B, time duration 530). In a seventh instance subsequent to the sixth instance, the method facilitates dispensing in the second fluid flow path 300 while the first fluid flow path 200 finishes dispensing, wherein in the seventh instance the first pump 204 is ramping down in speed and the second pump 304 is nearing the end of its ramping up in speed, wherein in the seventh instance both the first dispense valve 206 and the second dispense valve 306 are open, and both the first aspirate valve 202 and the second aspirate valve 302 are closed (see FIG. 4B, time duration 532). In an eighth instance subsequent to the seventh instance, the method facilitates dispensing in only the second fluid flow path 300, wherein in the eighth instance the first pump 204 is ramping down in speed and the second pump 304 is dispensing, wherein in the eighth instance the second dispense valve 306 is open and the second aspirate valve is closed 302, and wherein in the eighth instance the first dispense valve 206 is closed and the first aspirate valve 202 is open (see FIG. 4B, time duration 534). In a ninth instance subsequent to the eighth instance, the method continues to facilitate dispensing in only the second fluid flow path 300, wherein in the ninth instance the second pump 304 is dispensing and the first pump 204 is aspirating, wherein in the ninth instance the second dispense valve 306 is open and the second aspirate valve 302 is closed, and wherein in the ninth instance the first dispense valve 206 is closed and the first aspirate valve 202 is open (see FIG. 4B, time duration 536). In a tenth instance subsequent to the ninth instance, the method continues to facilitate dispensing in only the second fluid flow path 300, wherein in the tenth instance the second pump 304 is dispensing and the first pump 204 is waiting, wherein in the tenth instance the second dispense valve 306 is open and the second aspirate valve 302 is closed, and wherein in the tenth instance the first dispense valve 206 is closed and the first aspirate valve 202 is open (see FIG. 4B, time duration 538). In an eleventh instance subsequent to the tenth instance, the pumping cycle loops back to repeat the first through tenth instances (see FIGS. 4A and 4B, repetitive loop from time duration 538 to time duration 520).

As a result of the controlled fluid flow control devices with phase overlap events as herein disclosed, continuous or substantially continuous fluid flow at a defined constant flow rate is achievable.

FIG. 5 depicts an example motion diagram 600 for a single pump cycle with the on-off state diagrams for the corresponding aspirate and dispense valves, where trace 602 represents the on/off state of an aspirate valve (202 for example), trace 604 represents the cyclical position of a non-limiting example reciprocating pump (204 for example), and trace 606 represents the on/off state of a dispense valve (206 for example). In FIG. 5, the x-axis represents time, and the y-axis represents displacement or change of state, depending on the trace in question. At time 608, the aspirate valve 202 (via trace 602) switches from off to on, the pump 204 (via trace 604) switches from a positive stroke to a negative stroke, and the dispense valve 206 (via trace 606) switches from on to off. At time 610, the aspirate valve 202 (via trace 602) switches from on to off, the pump 204 (via trace 604) switches from a delay 612 after a negative stroke to a positive stroke, and the dispense valve 206 (via trace 606) switches from off to on. At time 614, the aspirate valve 202 (via trace 602) switches from off to on, the pump 204 (via trace 604) switches from a positive stroke to a negative stroke, and the dispense valve 206 (via trace 606) switches from on to off. At time 616, the aspirate valve 202 (via trace 602) switches from on to off, the pump 204 (via trace 604) switches from a delay 618 after a negative stroke to a positive stroke, and the dispense valve 206 (via trace 606) switches from off to on. The cycling and switching depicted in the motion diagram 600 of FIG. 5 is repeated for any desired number of repetitions.

FIG. 6 depicts an example motion diagram 700 for a dual pump cycle with the on-off state diagrams for the corresponding aspirate and dispense valves. Traces 602.1 and 602.2 represent the on/off states of first and second aspirate valves (202 and 302 for example), traces 604.1 and 604.2 represent the cyclical positions of a non-limiting example reciprocating pumps (204 and 304 for example), and traces 606.1 and 606.2 represent the on/off states of first and second dispense valve (206 and 306 for example). Traces 602.1, 604.1 and 606.1 of FIG. 6 are comparable to traces 602, 604 and 606 of FIG. 5. The times at 608, 610, 614, and 616, are comparable between FIGS. 5 and 6. As discussed herein above, to achieve the continuous or substantially continuous fluid flow at a defined constant flow rate, the first pump is set for dispensing while the second pump is set for aspirating, then a switch over occurs so that the first pump is set for aspirating while the second pump is set for dispensing, and during each switch over event both pumps are dispensing simultaneously for a defined period of time, which is herein referred to as a phase overlap and depicted in FIGS. 5 and 6 by reference numerals 620, 622, 624. Other similarities between the motion diagrams 600, 700 of FIGS. 5 and 6 will be readily understood by one skilled in the art without exhaustive further description being required herein.

Operational Sequence-1 outlines a start sequence for initiating pump dispensing, and a brief description of the pumping sequence.

The system 100 starts by homing the pumps, which involves:

1. Opening the corresponding dispense valve;

2. Moving the corresponding pump towards a home position and a home sensor, and stopping the pump when the home sensor is reached or activated;

3. Closing the corresponding dispense valve and opening the corresponding aspirate valve;

4. Moving the corresponding pump off of the home sensor a sufficient amount to provide the home sensor with some clearance; and

5. Closing the corresponding aspirate valve.

Additionally, the first pump is moved to full aspirate to get ready to begin cycling, which involves:

6. Opening the corresponding aspirate valve; and

7. Moving the first pump to full aspirate.

At this point, the first and second pumps are in position to begin cycling (both pumps are stopped and waiting to start), which involves, in order;

1. Pump 1 starts dispensing;

2. Pump 2 starts aspirating. Pump 2 aspirates faster than pump 1 dispenses to allow pump 2 to wait when it is done aspirating (see wait periods 612, 618 in FIG.5 for example);

3. When pump 1 gets into a phase overlap window (see phase overlaps 620, 624 in FIG. 6 for example), pump 2 begins accelerating up to speed to start dispensing;

4. Pump 2 starts dispensing while pump 1 is ramping down its speed;

5. Pump 1 starts aspirating. Pump 1 aspirates faster than pump 2 dispenses to allow pump 1 to wait when it is done aspirating; and

6. When pump 2 gets into a phase overlap window, pump 1 begins accelerating up to speed to start dispensing.

Each pump's aspirate and dispense valves' open and close times are adjustable, and during operation, the position of each pump is monitored, via controller 400 or an auxiliary sensor, and the valves are opened and closed as a set. Additionally, the speed, acceleration, and phase overlap associated with each pump are adjustable.

Operational Sequence-2 outlines steps of operation during pump dispensing.

In an embodiment of system 100, the pumps and valves may function as follows (in a loop):

1. Pump 1 starts dispensing while pump 2 is ramping down its speed to finish its dispense.

-   -   a. Pump 2 dispense valve closes.     -   b. Pump 2 aspirate valve opens to relieve any pressure from the         ramp down.

2. Pump 2 starts aspirating. Pump 2 aspirates faster than pump 1 dispenses to allow pump 2 to wait when it is done aspirating.

3. When pump 1 gets into a phase overlap window, pump 2 begins accelerating up to speed to start dispensing.

-   -   a. Pump 2 aspirate valve remains open for the initial         acceleration of the dispense cycle.     -   b. Pump 2 aspirate valve closes.     -   c. Pump 2 dispense valve opens.

4. Pump 2 starts dispensing while pump 1 is ramping down its speed to finish its dispense.

-   -   a. Pump 1 dispense valve closes.     -   b. Pump 1 aspirate valve opens to relieve any pressure during         the ramp down of the remaining dispense.

5. Pump 1 starts aspirating. Pump 1 aspirates faster than pump 2 dispenses to allow pump 1 to wait when it is done aspirating.

6. When pump 2 gets into a phase overlap window, pump 1 begins accelerating up to speed to start dispensing.

-   -   a. Pump 1 aspirate valve remains open for the initial         acceleration of the dispense cycle.     -   b. Pump 1 aspirate valve closes.     -   c. Pump 1 dispense valve opens.

7. A repeating loop of the steps 1-6 directly above may be performed a specified number of times as necessary to achieve the desired system performance and function.

Reference is now made to FIGS. 7-9, which depict empirical data of pressure signatures relating to an embodiment disclosed herein, where the pressure signatures were recorded just after (downstream of) the fluid restrictor 106, which is the location that represents the fluid input location to a downstream device requiring the steady pulseless flow. By way of example, FIGS. 7-9 were generated using an open loop dual stepper motor driven pump system, where a stepper motor (208, 308, 208′) can be moved continuously by a controller (400) through an arbitrary, integer number of discrete positions or ‘steps’, where it is common in the art to describe the stepper motor position, rate of rotation, and rate of acceleration, in units of [steps], [steps/sec], and [steps/sec²], respectively. In a non-limiting example embodiment, the term step used herein refers to an incremental rotational movement of 1.8-degrees of the corresponding stepper motor. For a comparison, the reader is invited to review FIG. 3 of U.S. Pat. No. 5,253,981, which depicts the pressure profile during a transition zone of a prior art system. As can be seen, the prior art transition zone includes both negative and positive pressure spikes, which in some applications is undesirable. In a negative/positive pressure spike situation, the negative pressure spike results from one pump slowing down before the second pump is at full pumping capacity, and the positive pressure spike results from both pumps pumping at the same time before one of them has ramped down. In contrast, FIGS. 7-9 depict output pressure characteristics that are capable of being achieved with an embodiment as disclosed herein. FIG. 7 depicts a resulting output pressure where one pump is pumping and the next pump starts pumping when the first pump has finished, with no phase overlap, and with a pump acceleration of about 185 steps/sec². As can be seen, a negative pressure spike occurs (proximate the 4 second mark) in the transition zone. FIG. 8 depicts a resulting output pressure where there is a 1500 millisecond phase overlap, with associated aspirate and dispense valve on/off times, and with a pump acceleration of 180 steps/sec². As can be seen, only a positive pressure spike results (proximate the 4 second mark), which in some applications is acceptable where the pressure just needs to stay above a threshold level. FIG. 9 depicts a resulting output pressure where there is an 800 millisecond phase overlap, with associated aspirate and dispense valve on/off time, and with a pump acceleration of 625 steps/sec². As can be seen, a minor pressure spike combination results (proximate the 2 second mark), which has a duration that is less than 1% of the overall pump cycle. FIG. 9 is considered herein to depict a continuous or substantially continuous flow output at a defined constant flow rate in accordance with an embodiment, which is not only the result of a favorable phase overlap, but also the result of a favorable pump acceleration.

From the foregoing, it will be appreciated that many options and benefits can be achieved using an embodiment as disclosed herein. For example, since the valves are active it is possible to run the pumps in reverse, taking fluid from outlet 104 and returning the fluid to the reservoir 110. This might be done as part of a cleaning cycle. In this instance fluid could first go through the system from inlet 102 to outlet 104, and then reversed from outlet 104 back to inlet 102. In another scenario the two pumps could be run at the same time. Under this case, while not continuous flow, the flow could be doubled to flush the system of air if needed during start-up. Another example is to cycle a pump while the aspirate valve is open all the time, and the dispense valve is closed. With this method it would be a possible to flush and wash the aspirate valve. Likewise the other valves could receive similar maintenance cycles. Other scenarios are contemplated where the first pump 204 could be dispensing while the second pump 304 is returning the fluid. All of the scenarios illustrate the flexibility of active valving in the system 100.

An embodiment may be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. In an embodiment, an apparatus for practicing those processes may be a control module, which may be a processor-implemented module or a module implemented by a computer processor, and may include a microprocessor, an ASIC, or software on a microprocessor. The present invention may also be embodied in the form of a computer program product having computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, USB (universal serial bus) drives, or any other computer readable storage medium, such as random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or flash memory, for example, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. The present invention may also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. A technical effect of the executable instructions is to adjust the operational characteristics of fluid flow control devices within a parallel arranged dual pump system to control the fluid flow during the transition of dispensing from one pump to another pump for continuous or substantially continuous fluid flow at a defined constant flow rate.

While an invention has been described herein with reference to example embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the claims. Many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment or embodiments disclosed herein as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In the drawings and the description, there have been disclosed example embodiments and, although specific terms and/or dimensions may have been employed, they are unless otherwise stated used in a generic, exemplary and/or descriptive sense only and not for purposes of limitation, the scope of the claims therefore not being so limited. The use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. The use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term “comprising” as used herein does not exclude the possible inclusion of one or more additional features. And, any background information provided herein is provided to reveal information believed by the applicant to be of possible relevance to the invention disclosed herein. No admission is necessarily intended, nor should be construed, that any of such background information constitutes prior art against an embodiment of the invention disclosed herein. 

1. A pump system, comprising: a first fluid flow path in fluid flow connection with an inlet path and an outlet path; a second fluid flow path in fluid flow connection with the inlet path and the outlet path; the first and second fluid flow paths being fluidly disposed in parallel with each other; the first fluid flow path comprising a first aspirate valve, a first pump disposed in series with and downstream of the first aspirate valve, and a first dispense valve disposed in series with and downstream of the first pump; the second fluid flow path comprising a second aspirate valve, a second pump disposed in series with and downstream of the second aspirate valve, and a second dispense valve disposed in series with and downstream of the second pump; wherein the first aspirate valve, the first pump, and the first dispense valve of the first fluid flow path, are configured to operate in both a dispense mode of operation and an aspirate mode of operation; wherein the second aspirate valve, the second pump, and the second dispense valve of the second fluid flow path, are configured to operate in both a dispense mode of operation and an aspirate mode of operation.
 2. The pump system of claim 1, wherein: the first pump is configured to dispense while the second pump is configured to aspirate, and subsequently, after a switchover window of time, the first pump is configured to aspirate while the second pump is configured to dispense, wherein during the switchover window of time both the first pump and the second pump are configured to dispense simultaneously for a defined period of time that defines a phase overlap of pump operation, wherein such pump operation including such phase overlap achieves continuous or substantially continuous fluid flow at a defined constant flow rate.
 3. The system of claim 1, wherein one or more of the first aspirate valve, the first dispense valve, the second aspirate valve, and the second dispense valve are diaphragm valves.
 4. The system of claim 1, wherein the outlet path comprises a fluid flow restrictor.
 5. The system of claim 1, wherein the inlet path is configured to receive fluid from a fluid reservoir.
 6. The system of claim 1, wherein in a first duration of time the first fluid flow path is configured to be in a dispense mode of operation while the second fluid flow path is configured to be in an aspirate mode of operation, and in a second duration of time the first fluid flow path is configured to be in an aspirate mode of operation while the second fluid flow path is configured to be in a dispense mode of operation.
 7. The system of claim 1, wherein: during the dispense mode of operation of the first fluid flow path, the first dispense valve is open and the first aspirate valve is closed; during the dispense mode of operation of the second fluid flow path, the second dispense valve is open and the second aspirate valve is closed; during the aspirate mode of operation of the first fluid flow path, the first dispense valve is closed and the first aspirate valve is open; and during the aspirate mode of operation of the second fluid flow path, the second dispense valve is closed and the second aspirate valve is open.
 8. The system of claim 1, wherein: the first aspirate valve, the first dispense valve, the second aspirate valve, and the second dispense valve, all have adjustable open and close times.
 9. The system of claim 1, wherein: both the first pump and the second pump have adjustable speed and acceleration characteristics.
 10. The system of claim 6, wherein in a third duration of time both the first fluid flow path and the second fluid flow path are configured to be in a dispense mode of operation.
 11. The system of claim 8, wherein in the third duration of time: both the first and second dispense valves are open; and both the first and second aspirate valves are closed.
 12. The system of claim 10, wherein: the third duration of time is adjustable in duration.
 13. The system of claim 10, further comprising a control module comprising a processing circuit responsive to executable instructions which when executed by the processing circuit is configured to adjust the first aspirate valve, the first pump, the first dispense valve, the second aspirate valve, the second pump, and the second dispense valve, according to the following method: in a first instance, facilitate a transition of dispensing from the second fluid flow path to dispensing from the first fluid flow path, wherein in the first instance the first pump starts ramping up in speed from a waiting state, wherein in the first instance the first aspirate valve is open, the first dispense valve is closed, the second aspirate valve is closed, and the second dispense valve is open; in a second instance subsequent to the first instance, facilitate dispensing in the first fluid flow path while the second fluid flow path finishes dispensing, wherein in the second instance the first pump is nearing the end of its ramping up in speed and the second pump is ramping down in speed, wherein in the second instance both the first dispense valve and the second dispense valve are open, and both the first aspirate valve and the second aspirate valve are closed; and in a third instance subsequent to the second instance, facilitate dispensing in only the first fluid flow path, wherein in the third instance the first pump is dispensing and the second pump is ramping down in speed, wherein in the third instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the third instance the second dispense valve is closed and the second aspirate valve open.
 14. The system of claim 13, wherein the method further comprises: in a fourth instance subsequent to the third instance, the method continues to facilitate dispensing in only the first fluid flow path, wherein in the fourth instance the first pump is dispensing and the second pump is aspirating, wherein in the fourth instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the fourth instance the second dispense valve is closed and the second aspirate valve is open; and in a fifth instance subsequent to the fourth instance, the method continues to facilitate dispensing in only the first fluid flow path, wherein in the fifth instance the first pump is dispensing and the second pump is waiting, wherein in the fifth instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the fifth instance the second dispense valve is closed and the second aspirate valve is open.
 15. A control module for controlling a dual pump system having a first fluid flow path having a series combination of a first aspirate valve, a first pump, and a first dispense valve, and a second fluid flow path having a series combination of a second aspirate valve, a second pump, and a second dispense valve, the first and second fluid flow paths being fluidly disposed in parallel with each other and having a common inlet path and a common outlet path, the control module comprising a processing circuit responsive to executable instructions which when executed by the processing circuit is configured to adjust the first aspirate valve, the first pump, the first dispense valve, the second aspirate valve, the second pump, and the second dispense valve, according to the following method: in a first instance, facilitate a transition of dispensing from the second fluid flow path to dispensing from the first fluid flow path, wherein in the first instance the first pump starts ramping up in speed from a waiting state, wherein in the first instance the first aspirate valve is open, the first dispense valve is closed, the second aspirate valve is closed, and the second dispense valve is open; in a second instance subsequent to the first instance, facilitate dispensing in the first fluid flow path while the second fluid flow path finishes dispensing, wherein in the second instance the first pump is nearing the end of its ramping up in speed and the second pump is ramping down in speed, wherein in the second instance both the first dispense valve and the second dispense valve are open, and both the first aspirate valve and the second aspirate valve are closed; and in a third instance subsequent to the second instance, facilitate dispensing in only the first fluid flow path, wherein in the third instance the first pump is dispensing and the second pump is ramping down in speed, wherein in the third instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the third instance the second dispense valve is closed and the second aspirate valve open.
 16. The control module of claim 15, wherein the method further comprises: in a fourth instance subsequent to the third instance, the method continues to facilitate dispensing in only the first fluid flow path, wherein in the fourth instance the first pump is dispensing and the second pump is aspirating, wherein in the fourth instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the fourth instance the second dispense valve is closed and the second aspirate valve is open; and in a fifth instance subsequent to the fourth instance, the method continues to facilitate dispensing in only the first fluid flow path, wherein in the fifth instance the first pump is dispensing and the second pump is waiting, wherein in the fifth instance the first dispense valve is open and the first aspirate valve is closed, and wherein in the fifth instance the second dispense valve is closed and the second aspirate valve is open. 